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Transcriptional response to Wnt activation regulates the regenerative capacity of the mammalian cochlea.

ABSTRACT: Lack of sensory hair cell (HC) regeneration in mammalian adults is a major contributor to hearing loss. In contrast, the neonatal mouse cochlea retains a transient capacity for regeneration, and forced Wnt activation in neonatal stages promotes supporting cell (SC) proliferation and induction of ectopic HCs. We currently know little about the temporal pattern and underlying mechanism of this age-dependent regenerative response. Using an in vitro model, we show that Wnt activation promotes SC proliferation following birth, but prior to postnatal day (P) 5. This age-dependent decline in proliferation occurs despite evidence that the Wnt pathway is postnatally active and can be further enhanced by Wnt stimulators. Using an in vivo mouse model and RNA sequencing, we show that proliferation in the early neonatal cochlea is correlated with a unique transcriptional response that diminishes with age. Furthermore, we find that augmenting Wnt signaling through the neonatal stages extends the window for HC induction in response to Notch signaling inhibition. Our results suggest that the downstream transcriptional response to Wnt activation, in part, underlies the regenerative capacity of the mammalian cochlea.

SUBMITTER: Samarajeewa A

PROVIDER: S-EPMC6288390 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Transcriptional response to Wnt activation regulates the regenerative capacity of the mammalian cochlea.

Samarajeewa Anshula A Lenz Danielle R DR Xie Lihong L Chiang Hao H Kirchner Rory R Mulvaney Joanna F JF Edge Albert S B ASB Dabdoub Alain A

Development (Cambridge, England) 20181127 23

Lack of sensory hair cell (HC) regeneration in mammalian adults is a major contributor to hearing loss. In contrast, the neonatal mouse cochlea retains a transient capacity for regeneration, and forced Wnt activation in neonatal stages promotes supporting cell (SC) proliferation and induction of ectopic HCs. We currently know little about the temporal pattern and underlying mechanism of this age-dependent regenerative response. Using an <i>in vitro</i> model, we show that Wnt activation promotes ...[more]

PMID: 30389848

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Project description:Purpose: Wnt activation can induce regeneration in the early postnatal cochlea, but the regenerative capacity of the postnatal cochlea diminishes between P0 to P5. The goal of this study was to utilize RNA-Seq for the overall evaluation of expression patterns, comparing P1 and P4 newborn cochlea with and without Wnt activation. Methods: Sox2-CreER; β-cateninflox(Exon3)/+ mice were used to stabilize β-catenin in Sox2+ cochlear supporting cells. Tamoxifen was injected to the mother at either P1 or P4 to induce Cre activation in the pups. mRNA libraries were generated from treated and untreated pups 3 days after injection in triplicates (overall 12 samples) using ThruPLEX DNA-seq kit (Rubicon Genomics) and then sequenced using Illumina NextSeq500 Single-End 75bp. Reads were aligned to mm10 and quality control was assessed using FastQC and Qualimap followed by FeatureCounts, Sailfish v0.10.1 and tximport. Differential expression was evaluated using DESeq2 and subsequent pathway analysis was performed using Ingenuity Pathway Analysis Software (Qiagen). Results: 40-50 million reads were detected per sample. PCA and Pearson correlation demonstrated a clear segragation of the samples by age that was supported by the identification of 2914 differentially expressed genes between P1 and P4 samples. Additional affect of treatment resulted is 530 differentially expressed genes between treated and untreated samples at P1 and 304 genes were differentially expressed between treated and untreated samples at P4. Clear activation of the Wnt pathway was apparent at both time-points after treatment. However, activation of downstream pathways that may be involved in regeneration was detected at P1 but not at P4, mainly the involvement of cell-cycle and proliferation as well as Erbb2 associated genes. Conclusions: Our results suggest that the Wnt pathway is still active and can be further induced at early and late postnatal stages in a similar manner. However, at early stages, exogenous Wnt activation potentially promotes an arrest of maturation progression or even partial dedifferentiation of supporting cells into a less mature state that enables regeneration, while the downstream affect is not as prominenet later on. Proliferative capacity in the early postnatal cochlea is correlated with a unique transcriptional response that diminishes in the older cochlea, including a robust increase in the expression of cell cycle genes and cellular growth and development genes. Our results suggest that the downstream transcriptional response to Wnt activation is the key factor mediating a regenerative response, or a lack-thereof, in the mammalian cochlea and that efforts to stimulate regeneration in the adult auditory organ may require recapitulating the transcriptional response of the early neonatal cochlea to exogenous Wnt activation and subsequent alterations of silenced state of Wnt target genes. .

Dataset Information

Transcriptional response to Wnt activation regulates the regenerative capacity of the mammalian cochlea.

Publications

Transcriptional response to Wnt activation regulates the regenerative capacity of the mammalian cochlea.

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